Data processing systems are usually provided with a graphical user interface (GUI) to allow a user to control the data processing system and to present the results of user actions on the system display. In a graphical user interface, applications and data are generally presented as objects depicted on a user interface. A user is then provided with a graphical, intuitive interface to a complex data processing system which permits graphic selection of depicted objects and manipulation of applications corresponding to those objects.
It is usually possible to simultaneously execute several software applications. The execution of multiple applications simultaneously is often referred to as "multitasking". It is desirable in such environments to allow the user to view some or all of the applications simultaneously. This is often accomplished by the utilization of the concept of "windows" wherein all or part of multiple applications are displayed in separate viewports of a computer system video display system. It is known to have multiple software applications present on a computer display simultaneously, one or more of which may be active at any given time, and which may be displayed in a window or icon.
There may be several windows simultaneously present on the desktop with each window displaying information that is generated by a different application program. Each application program presents information to the user through its window by drawing images, graphics or text within the window region. The user, in turn, communicates with the application by pointing at graphical objects in the window with a pointer that is controlled by a pointing device, such as a mouse, and then selecting the objects, or by typing information via a keyboard associated with the monitor. Selection of the objects may be effected by actuating the mouse to move the pointer onto or near the objects and pressing and quickly releasing, i.e. clicking, a button on the mouse, or by manipulating a cursor via the keyboard.
These user interface objects may be easily manipulated utilizing a standard set of interface commands. For example, the user may move the windows around on the display screen, change their sizes and appearances, shrink down a window to a so-called icon, rearrange the objects with respect to their relative background/foreground position so as to arrange the desktop in a convenient manner, etc.
There are a number of different graphical user interface environments commercially available which utilize the arrangement described above. These environments include the System 7 operating system developed by Apple Computer, Inc. (System 7 is a trademark of Apple Computer, Inc.), the Windows graphical user interface developed by the Microsoft Corporation (Windows is a trademark of Microsoft Corporation) and the OS/2 Presentation Manager developed by International Business Machines Corporation (OS/2 and Presentation Manager are trademarks of International Business Machines Corporation).
As mentioned above one of the possible operations a user can perform on a window is to change its size. This is usually accomplished by placing the cursor, using the mouse or any pointer device, on a side or on a corner of the window, "dragging" the border, i.e. associating the border of the window to the cursor so that the moving of the cursor will cause the border to move, and moving the side or the corner of the window causing the window to resize accordingly.
Of course when the window has reached its maximum or minimum limit, the border (either through a side or a corner) cannot be moved further. The known graphical user interfaces have the drawback that there is no signal to the user which clearly informs of the impossibility of further resizing in that direction. So there is no way for the user to immediately understand he is trying an impossible operation. The only feedback the system provides to the user is that nothing happens while the user tries the resizing. This could be misleading because it is quite easy to "miss" the window border during the dragging operation; it so highly probable that the user will try again repeatedly before being sure the limit size has been reached.
It is an object of the present invention to provide a technique which alleviates the above drawbacks.